F Units on the NS

My office in Harrisburg overlooks the NS main (ex PRR) just West the Amtrak station. At about 4:30 PM today, 09/26/17, I spotted through the trees a NS unit pulling a classic string F units in an A-B-A set-up and nothing else heading West out of Harrisburg. The F's look to be black with white (?) or silver (?) classic F unit striping. While too far away, and too many trees, the RR name looked to be in gold. Any idea of what I sow and where they were headed?